Current take-off unit

ABSTRACT

A current take-off unit is provided which may be readily connected to or disconnected from an external current-carrying element. The unit includes a housing having an opening formed in a wall thereof. The housing is positioned so that the wall opening is disposed adjacent the external element. A conductor means is disposed within the housing and has a portion thereof terminating at the wall opening. Adjustably mounted on the terminating portion of the conductor means is a connector assembly which is adapted to be moved between extended or retracted positions relative to the wall opening. The assembly includes a pair of conductive jaw members which are adapted to project through the wall opening and grippingly engage the external current-carrying element. The assembly also includes an elongated member which extends transversely through the jaw members and conductor means portion and retains same in an assembled relation. The elongated member carries a manually adjustable means which when adjusted in one direction causes the jaw members to move towards one another into gripping engagement with the external element. When the adjustable means is manually adjusted in a second direction, the jaw members can be moved out of gripping relation, whereby the jaw members can assume either an extended or retracted position.

United States Patent [191 Reed et al.

[451 Sept. 30, 1975 CURRENT TAKE-OFF UNIT [75] Inventors: Ronald B. Reed, Versailles; Joseph C. Drilling; Lary D. Jones, both of Lexington, all of Ky.

[73] Assignee: Square D Company, Park Ridge, [IL

[22] Filed: Apr. 25, 1974 [21] Appl. No.: 464,280

Prinmry E.\'amine/'Joseph H. McGlynn Assistant E.\-uminerCraig R. Feinberg Attorney, Agent, or Firm-Ernest S. Kettelson; Harold J. Rathbun [57] ABSTRACT A current take-off unit is provided which may be readily connected to or disconnected from an external current-carrying element. The unit includes a housing having an opening formed in a wall thereof. The housing is positioned so that the wall opening is disposed adjacent the external element. A conductor means is disposed within the housing and has a portion thereof terminating at the wall opening. Adjustably mounted on the terminating portion of the conductor means is a connector assembly which is adapted to be moved between extended or retracted positions relative to the wall opening. The assembly includes a pair of conductive jaw members which are adapted to project through the wall opening and grippingly engage the external current-carrying element. The assembly also includes an elongated member which extends transversely through the jaw members and conductor means portion and retains same in an assembled relation. The elongated member carries a manually adjustable means which when adjusted in one direction causes the jaw members to move towards one another into gripping engagement with the external element. When the adjustable means is manually adjusted in a second direction, the jaw members can be moved out of gripping relation, whereby the jaw members can assume either an extended or retracted position.

18 Claims, 13 Drawing Figures U.S. Patent Sept. 30,1975 Sheet 1 of 3 3,909,098

U.S. Patent Sept. 30,1975 Sheet 2 of3 3,909,098

US. Patent Sept. 30,1975 Sheet 3 of3 3,909098 CURRENT TAKE-OFF UNIT BACKGROUND OF THE INVENTION l-leretofore in the installation or replacement of current take-off units, such as meter units and the like, numerous difficulties were oftentimes encountered. Examples of such difficulties were (a) oftentimes because of the unit configuration it was necessary to connect the unit to the external current-carrying member, e.g., bus bars, before the unit was permanently mounted on a supporting surface; (b) where several units were arranged in ganged or side-by-side relation, it was necessary when removing a given unit to also remove the adjacent units from the main bus bars; and several separate components were required to install the unit thereby resulting in the installation being a complex, awkward and time-consuming operation.

SUMMARY OF THE INVENTION Thus, it is an object of the invention to provide a current take-off unit which is of simple construction and has self-contained connecting means for readily connecting the unit to an external current-carrying element.

It is a further object of the invention to provide a current take-off unit which can be readily installed in or removed from a run of units arranged in side-by-side relation without requiring the removal disconnection of a plurality of the other units comprising the run.

It is a still further object of the invention to provide a unit which may be permanently mounted on a supporting surface before the unit is connected to the external current-carrying element.

It is a still further object of the invention to provide a self-contained unit which when installed in a run with other units is provided with means for readily interrupting current flow to only part of the units forming the run.

It is a still further object of the invention to provide a unit which may be readily installed when utilizing only conventional tools.

Further and additional objects will appear from the description, accompanying drawings, and appended claims.

In accordance with one embodiment of the invention, a current take-off unit is provided which is adapted to be removably connected to an external current-carrying element. The unit includes a housing having a wall thereof provided with an opening. The housing is mounted on a supporting surface so that the wall opening is in close proximity to the external currentcarrying element. The unit also includes a conductor means disposed within the housing and having a portion thereof terminating at the wall opening. A connector assembly is adjustably mounted on the terminating portion of the conductor means for movement between extended and retracted positions relative to the wall opening. The connector assembly includes at least one pair of elongated jaw members formed of conductive material and an elongated member disposed transversely of and through the jaw members and the conductor means terminating portion so as to retain same in assembled relation. The elongated member includes manually adjustable means which, when adjusted in one direction and when the jaw members are disposed in an extended position, will cause relative movement of the jaw members towards one another into gripping engagement with the external current-carrying element. The jaw members when in gripping relation span the distance between the external element and the terminating portion of the conductor means disposed within the housing.

DESCRIPTION For a more complete understanding of the invention, reference should be made to the drawings wherein:

FIG. 1 is a fragmentary perspective view of one form of the improved units shown mounted in juxtaposed relation and forming a run.

FIG. 2 is an enlarged fragmentary perspective view of the connector assembly of FIG. 1 shown connecting adjacent units.

FIG. 3 is a front elevational view of FIG. 2, but showing the connector assembly of one unit in a retracted position relative to the wall opening.

FIG. 4 is an exploded, fragmentary, perspective view of a plurality of the components comprising the connector assembly of FIGS. 2 and 3.

FIGS. 5 and 6 are fragmentary sectional views taken along line 5 -5 and 6-6, respectively, of FIG. 3.

FIG. 7 is a perspective view of an insulating piece forming a component of the connector assembly and disposed intermediate adjacent pairs of jaw members.

FIGS. 8 and 9 are sectional views taken along lines 88 and 99, respectively, of FIG. 7.

FIG. 10 is similar to FIG. 7 but showing a second form of insulating piece.

FIGS. 11 and 12 are sectional views taken along lines l1-11 and 12-l2, respectively, of FIG. 10.

FIG. 13 is a perspective view of one form of a jaw member.

Referring now to the drawings and more particularly to FIG. 1, one form of an improved current take-off unit is shown disposed in juxtaposed relation with a like unit 120. Each unit 20 or 120, as illustrated, is of similar construction and therefore only unit 20 will be described in detail. Corresponding parts of units 20 and 120 will be numbered the same except that in unit 120, the parts will be numbered in the one hundred series. Unit 20 includes a housing 21 having a back wall panel 22 adapted to be fixedly mounted on a supporting surface, not shown, by suitable fasteners or the like.

Projecting transversely outwardly from panel 22 is a pair of side wall panels 23 and 24. The wall panels 23 and 24 are of planar configuration and are disposed in spaced substantially parallel relation. The outer edge 23a and 24a of the wall panels are tranversely offset towards one another so as to provide a backing surface for a housing front panel, not shown, which is removably secured thereto by suitable fasteners. The front panel may be of conventional design and provided with suitable openings for accommodating meters or the like. It will be noted in FIG. 1 embodiment that each side wall panel is provided with an opening 23b or 24b of like configuration.

Disposed within the housing and positioned in close proximity to, but spaced from, the back wall panel 22 is a conductor means 25 which in the illustrated embodiment comprises a plurality of flat bus bars 26, 27, 28 and 29 arranged in spaced, parallel relation. Each bus bar is of like configuration and has a length slightly less than the spacing between the wall panels 23 and 24. The spacing between adjacent bars is maintained by conventional insulated spacers, not shown, but well understood in the art.

It is important in the illustrated embodiment that the corresponding ends of the bars be disposed in close.

proximity to the respective wall panel opening 23b or 24b.

Adjustably mounted on the respective ends'of the bars disposed adjacent one of the wall panels (e.g., panel 23, as seen in FIG. 1) is a connector assembly 30.

As seen more clearly in FIGS. 4-6, one form of the assembly 30 includes pairs of jaw members 31, 32, 33 and 34. One jaw member 31a of the pair 31 of jaw members and representative of allthe jaw members is shown in FIG. 13. The number of pairs ofjaw members included in the connector assembly 30 will depend on the number of bus bars comprising the conductor means 24. Disposed intermediate adjacent pairs of jaw members are interior or first insulating members 35, one of which is shown in FIGS. 7-9. The outermost jaw member 31a of the pair 31 of the jaw members and the outermost jaw member 34a of the pair 34 of jaw members are engaged by outer or second insulating members 36, one of the latter being shown in FIGS. 10-12. The jaw members and the insulating members are retained in their proper relation by an elongated retaining bolt-like member 37. One end 37a of member 37 is threaded and is adapted to be engaged by a nut 38. Disposed between the nut and the insulating member 36 is a pair of washers 40 and 41. The opposite end of member 37 is provided with an enlarged head 37b. Disposed between head 37b and the other outermost insulating member 36 is another similar pair of washers 42 and 43. As the nut 38 is manually drawn up tight on the end 37a of member 37, the pairs ofjaw members will be moved towards one another a predetermined amount, whereby, when the assembly 30 is in an extended position, will grippingly engage the external current-carrying element. In the illustrated embodiment, the external current-carrying element comprises the conductor means 125 of the adjacent unit 120, see FIGS. 1 and 2.

Movement endwise of the connector assembly 30 to extended and retracted positions relative to the bus bars comprising the conductor means 25 is facilitated by the open end, elongated slots 26a, 27a, 28a and 29a formed in the corresponding ends of the bus bars 26, 27, 28 and 29.

The jaw member 31a shown in FIG. 13 is representative of the various jaw members comprising the pairs of jaw members previously mentioned and shown in FIGS. and 6. Jaw member 31a is formed of a suitable conductive material and is provided with an enlarged opening 31b through which the bolt-like member 37 and a portion of the insulating member extend in a manner to be hereinafter described. A peripheral slot 310 is also formed in the jaw member. When the jaw member is mounted on the conductor means 25,the slotted peripheral side of the member faces inwardly away from the wall opening 23b. It will be noted that the opening 31b is offset from the center toward the slotted periphcry, thereby resulting in the portion of the jaw member disposed to the right ofthe opening 31b, as seen in FIG. 13 having the greater length. It is this latter portion of the jaw member which projects towards the external current-carrying element.

The outermost insulating member 36, shown in FIGS. -12, is adapted to be mounted so as to engage the outer surface of either jaw member 31a or 34a. Member 36 has a general peripheral configuration similar to that ofjaw member 31a or 34a; however, member 36 is provided with a peripheral flange 360 which is adapted to substantially encompass the jaw member when assembled therewith. The extent to which the flange 36a protrudes is less than the thickness of the jaw member and, thus, when the nut 38 is tightened on.

the end of the member, the jaw member will positively engage simultaneously the corresponding bus bars 26, 126 or 29, 129.

It will be noted in FIG. 10 that the flange 36a is interrupted by a projection 36b which is adapted to extend through the slot 310 of the jaw member 31a. The projection has a peripheral shape which closely resembles the slot 310 and, thus, when the projection is disposed.

within the slot the jaw member and insulating member will be properly oriented relative toone another. Member 36 is provided with an opening 360, see FIG. 12,' which is delimited on one side of the member by an annular collar 36d. The. exterior configuration of the collar 36d is such that it will extend through the opening 31b formed in jaw member 310 or opening 34b ofjaw member 34a. The collar 36d insulates the member 37 from the jaw member, see FIGS. 5 and 6.

The outer or exterior surface of insulating member 36 is preferably provided with a plurality of locating pinlike projections 44, see FIG. 4, which are adapted to locate the washer 41 or 43, see FIGS. 5 and 6.

The inner insulating members 35 are similar in construction to members36, except that in each member 35, the opposite faces thereof are the same as the inner face of member 36, shown in FIG. 10. That isto say, the peripheral flange 35a, the projection 35b, and the collar 35d extend the same amount from opposite faces of member 35 see FIGS. 7, 8 and 9. The inner members 35 can serve to insulate one pair ofjaw members from an adjacent pair of jaw members, as seen more clearly in FIGS. 5 and 6. The shape of the jaw members. and the inner and outer insulating members may vary from that shown without departing from the scope of the invention.

Because of the collars of the insulating members being properly sized so as to fit .into the openings formed in the jaw members, the jaw members, the insu-:

lating members, the rod-like member and nut, andthe washers can be manually movedas a unit longitudinally of the bus bar slots provided the nut 38 is not drawn up tight on the end 37a of the member 37.

When the unit is being installed, the connector asseembly 30 is adjusted so as to assume retracted position as seen in FIG. 3. The housing 31 is mounted on a supporting surface so that the wall opening 23b is disposed in close proximity to the external currentcarrying element, which in the FIG. 1 embodiment is the opening 124b (see FIG. 2) formed in the housing wall 124, and the end of the conductor means 125 adjacent the opening. The openings 23b and l24b are of like configuration and the bus bars comprising the conductor means 26 and 27 are disposed in axially aligned relation, see FIG. 2. Once the corresponding bus bars of the conductor means and 125 are in proper alignment, the tightening nut 38 is loosened thereby enabling the connector "assembly to be manually shifted to the right from the retracted position shown in FIG. 3 to the extended position, shown in FIG. 2. When the assembly is in its extended position, the pair of jaw members 31 will sandwich therebetween the bus bar 26 of conductor means and the corresponding bus bar of conductor means 125. In a like manner, the pair of jaw members 32 sandwiches bus bar 27 and its counterpart 127, the pair of jaw members 33 sandwichs bus bar 28 and its counterpart 128 and the pair of jaw members 34 sandwiches bus bar 29 and its counterpart 129. Once the components of the connector assembly 30 are in their proper relative position with respect to the conductor means 25 and 125, the nut 38 is drawn up tight thereby causing the jaw members to grippingly engage the corresponding bus bars and, thus, make proper electrical contact. A torque wrench may be employed for drawing up the nut so as to control the ultimate amount of torque applied to the nut.

While the nut 38 is shown facing outwardly so as to be accessible for tightening, it may be preferred to reverse the position of the bolt-like member 37 so that the head 37b thereof is exposed. In the latter arrangement, it might be desirable to have the head 37b of the well-known twist-off type. In such a head type, a secondary head is spaced axially outwardly from the primary head which is connected directly to the end of the member shank. The two heads are interconnected by a narrow stem-like portion which will fracture when a predetermined torque is applied to the secondary head.

When the unit is to be removed from the line, the reverse procedure should be followed. The longitudinal length of the open end slots formed in the bus bars 26-29 should be such that, when the connector assembly is in its retracted position, FIG. 3, all of the components comprising the assembly will be recessed from the wall 23.

As seen in FIG. 2, the exposed surface of the outer insulating member 36 may be provided with a guide mark M, which is vertically disposed. When the mark M is visually aligned with the interior surface of the housing wall 23, the installer will know that the assembly 30 is disposed in its proper extended position.

While the improved unit 20 is shown assembled in ganged relation with a similar unit 120, it is to be understood that the invention is not limited thereto. Thus, the external current-carrying element may take many other forms. The number and shape of the bus bars 7 comprising the conductor means disposed within the housing may also be varied.

Thus, it will be seen that an improved current takeoff unit has been provided which embodied a selfcontained connector assembly, and may be readily mounted on a supporting surface before the unit is connected to an external current-carrying element. The unit may be installed in ganged relation with like units without requiring disconnecting of or removal of several of the adjacent units in the gang. The unit may be installed on or removed from the supporting surface and the external current-carrying element without requiring special tools.

We claim:

1. A current take-off unit adapted to be removably connected to an external current carrying element, said unit comprising a housing having an opening formed in a wall thereof and being positionable adjacent to the external current-carrying element; conductor means within said housing and having an end portion thereof disposed adjacent said opening and terminating short of the adjacent region outwardly of said opening; and a connector assembly adjustably mounted on the conductor means end portion for movement between extended and retracted positions relative to said housing opening, said assembly including a pair of conductive jaw members adapted to assume a gripping engagement with the external current-carrying element when said connector assembly is in said extended position whereby said jaw members span the distance between the external current-carrying element and the end portion of said conductor means, an elongated member extending transversely through apertures formed in said jaw member and through the end portion of said conductor means and being in non-conductive relation therewith and retaining same in assembled relation, and manually adjustable to means carried by said elongated member and adapted, when adjusted in one direction, to effect relative movement to said jaw members towards one another into gripping relation with the current-carrying element when said connector assembly is in said extended position.

2. The current take-off unit of claim 1 wherein said jaw members are sandwiched between insulating means.

3. The current take-off unit of claim 2 wherein the jaw members are elongated planar pieces of conductive material and are provided with aligned apertures through which the elongated member transversely extends, and said insulating means includes planar sections of insulating material disposed in face-to-face relation with the outer surfaces of said planar pieces, said planar sections being provided with apertures aligned with the apertures of said pieces and through which the elongated member transversely extends.

4. The current take-off unit of claim 3 wherein the end portion of the conductor means adjacent the wall opening is provided with an elongated slot disposed substantially transversely of said housing wall; said elongated member extending through said slot and being movable longitudinally thereof when said manually adjustable means carried by said elongated member is adjusted in a second direction.

5. The current take-off unit of claim 3 wherein at least one planar section is provided with a protuberance which is adapted to extend transversely of a planar piece and abuttingly engage the other planar section when said planar pieces are in gripping engagement with the external current-carrying element.

6. The current take-off unit of claim 3 wherein the aperture formed in each planar piece is sized to accommodate a protruding collar formed on the adjacent planar section, said collar delimiting the aligned aperture formed in said adjacent planar section.

7. The current take-off unit of claim 1 wherein said conductor means comprises a plurality of elongated bus bars arranged in spaced substantially parallel relation and extending substantially transversely of said housing wall opening, corresponding ends of said bus bars being adjacent said wall opening and each of said ends being provided with an elongated longitudinally extending slot; said connector assembly including a pair of conductive jaw members for each bus bar, each pair of jaw members being separated from an adjacent pair of jaw members by insulating means.

8. The current take off unit of claim 7 wherein the insulating means includes a planar section of insulating material disposed intermediate adjacent pairs of jaw members, said planar section being provided. with an aperture through which transversely extends the elongated member; said planar section aperture being delimited by a protruding collar which extends into the aligned aperture formed in the adjacent jaw member.

9. A current take-off unit adapted to be removably connected to an external current-carrying element and movable transversely of said external current-carrying element into and out of position for aligned connection therewith, said unit comprising bus bar means, said bus bar means including free end means for end-to-end alignment with corresponding free ends means of said external current-carrying element, said respective free end means terminating short of each other when in said end-to-end alignment, a connector assembly adjustably mounted on said bus bar means for longitudinal movement between extended and retracted positions relative to said free end means of said bus bar means, said connector assembly including conductive means adapted for electrically conductive engagement with said external current-carrying element when said connector assembly is in said extended position whereby said conductive means spans the distance between the said free end means of said external current-carrying element and the said free end means of said bus bar means, an elongated member extending transversely through apertures formed in said conductive means and through said bus bar means in the region of said free end means thereof and being in non-conductive relation therewith and retaining same in assembled relation, and manually adjustable means carried by said elongated member and adapted, when adjusted in one direction, to effect a gripping relation of said conductive means with said current carrying element when said connector assembly is in said extended position.

10. A current take-off unit adapted to be removably connected to a current-carrying installation at an intermediate location between a source side current carrying element and a load side current-carrying element, said unit being movable transversely of said source side and load side current-carrying elements into and out of position for aligned connection therewith, said unit comprising bus bar means, said bus bar means including first and second free end means at opposite ends thereof for end-to-end alignment with corresponding free end means of said source side currentcarrying element and of said load side current carrying element respectively, said respective free end means terminating short of each other when in said end-to-end alignment, a connector assembly adjustably mounted,

on said bus bar means in the region of said first free end means for longitudinal movement between extended and retracted positions in relation to said first free end means, said connector assembly including conductive means adapted for electrically conductive engagement with said free end means of one of said source-side and said load side current-carrying elements when said connector assembly is in said extended position whereby said conductive means spans the distance between the said free end means of said current-carrying element and the first free end means of said bus bar means, an elongated member extending transversely through apertures formed in said conductive means and through said bus bar means in the region of said first free end means thereof and being in non-conductive relation therewith retaining same in assembled relation, and

manually adjustable means carried by said elongated member andradapted, when adjusted in one direction,

to effect a gripping relation of said conductive means with said current-carrying element when said connector assembly is in said extended position.

11. A current take-off unit as set forth in claim 10, including a second of said connector assemblies adjustably mounted for connecting association between, and

on one of, said second free end means of said bus bar means and the free end means of the other of said source-side and, load-side current carrying elements,

12., A current take-off. unit as set forth in claim 9,

wherein said conductive means include a pair of conductive jaw members, said jaw members being sandwiched between insulating means.

13. A current take-off unit as set forth in claim 12,

wherein said jaw membersare elongated planarpieces, of conductive material and are provided with aligned tures aligned with the apertures of said pieces and' through which the elongated member transversely extends.

14. A current take-off unit as set forth in claim, 13,

wherein'said free end means of said bus bar means is provided withan elongated slot, said elongated member extending through said slot and being movable longitudinally thereof when said manually adjustable means carried by said elongated member is adjusted in a second direction.

15. A current take-off unit as set forth in claim 13, wherein at least one planar section is provided with a protuberance which is adapted to extend transversely of a planar piece and abuttingly engage the other planar section when said planar pieces are in gripping engagement with the external current-carrying element.

16. A current take-off unit as set forthin claim 13, wherein said aperture formed in each planar piece is sized to accommodate a protruding collar formed on the adjacent planar section, said collar delimiting the aligned aperture formed in said adjacent planar section.

17. A current take-off unit as forth in claim 9, wherein said bus bar means includes a plurality of elongated bus bars arranged in spaced substantially parallel relation, elongated lontigudinally extending slots in the free ends of each of said bus bars, said connector assembly including a pair of conductive jaw members for each bus bar, each pair of jaw members being sepa rated from an adjacent pair of jaw members by insulating means.

18. A current take-off unit as set forth in claim 17, wherein said insulating means includes a planar section of insulating material disposed intermediate adjacent pairs of jaw members, said planar. section being provided with an aperture through which transversely extendsthe elongated member, said planar section apera ture being delimited by a protruding collar which extends into the aligned aperture formed in the adjacent jaw member.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,909,098 DATED September 30, 1975 |NV ENTOR( )I R. H. Reed, J. C. Drilling & L. D. Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 28 after removal insert -or. Column 4, line 52 after assume insert a-. Column 4, line 61 mange "27" and insert l26. Column 5, line 49 change "embodied" to embodies-. Column 6, line 11 change "member" to --members-. Column 6, line 14 after adjustable delete "to". Q

Signed and Scaled this Y sixth D y of January 1976 [SEAL] Arrest:

O RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner nfPatenls and Trademarks 

1. A current take-off unit adapted to be removably connected to an external current carrying element, said unit comprising a housing having an opening formed in a wall thereof and being positionable adjacent to the external current-carrying element; conductor means within said housing and having an end portion thereof disposed adjacent said opening and terminating short of the adjacent region outwardly of said opening; and a connector assembly adjustably mounted on the conductor means end portion for movement between extended and retracted positions relative to said housing opening, said assembly including a pair of conductive jaw members adapted to assume a gripping engagement with the external current-carrying element when said connector assembly is in said extended position whereby said jaw members span the distance between the external current-carrying element and the end portion of said conductor means, an elongated member extending transversely through apertures formed in said jaw member and through the end portion of said conductor means and being in non-conductive relation therewith and retaining same in assembled relation, and manually adjustable to means carried by said elongated member and adapted, when adjusted in one direction, to effect relative movement to said jaw members towards one another into gripping relation with the currentcarrying element when said connector assembly is in said extended position.
 2. The current take-off unit of claim 1 wherein said jaw members are sandwiched between insulating means.
 3. The current take-off unit of claim 2 wherein the jaw members are elongated planar pieces of conductive material and are provided with aligned apertures through which the elongated member transversely extends, and said insulating means includes planar sections of insulating material disposed in face-to-face relation with the outer surfaces of said planar pieces, said planar sections being provided with apertures aligned with the apertures of said pieces and through which the elongated member transversely extends.
 4. The current take-off unit of claim 3 wherein the end portion of the conductor means adjacent the wall opening is provided with an elongated slot disposed substantially transversely of said housing wall; said elongated member extending through said slot and being movable longitudinally thereof when said manually adjustable means carried by said elongated member is adjusted in a second direction.
 5. The current take-off unit of claim 3 wherein at least one planar section is provided with a protuberance which is adapted to extend transversely of a planar piece and abuttingly engage the other planar section when said planar pieces are in gripping engagement with the external current-carrying element.
 6. The current take-off unit of claim 3 wherein the aperture formed in each planar piece is sized to accommodate a protruding collar formed on the adjacent planar section, said collar delimiting the aligned aperture formed in said adjacent planar section.
 7. The current take-off unit of claim 1 wherein said conductor means comprises a plurality of elongated bus bars arranged in spaced substantially parallel relation and extending substantially transversely of said housing wall opening, corresponding ends of said bus bars being adjacent said wall opening and each of said ends being provided with an elongated longitudinally extending slot; said connector assembly including a pair of conductive jaw members for each bus bar, each pair of jaw members being separated from an adjacent pair of jaw members by insulating means.
 8. The current take-off unit of claim 7 wherein the insulating means includes a planar section of insulating material disposed intermediate adjacent pairs of jaw members, said planar section being provided with an aperture through which transversely extends the elongated member; said planar section aperture being delimited by a protruding collar which extends into the aligned aperture formed in the adjacent jaw member.
 9. A current take-off unit adapted to be removably connected to an external current-carrying element and movable transversely of said external current-carrying element into and out of position for aligned connection therewith, said unit comprising bus bar means, said bus bar means including free end means for end-to-end alignment with corresponding free ends means of said external current-carrying element, said respective free end means terminating short of each other when in said end-to-end alignment, a connector assembly adjustably mounted on said bus bar means for longitudinal movement between extended and retracted positions relative to said free end means of said bus bar means, said connector assembly including conductive means adapted for electrically conductive engagement with said external current-carrying element when said connector assembly is in said extended position whereby said conductive means spans the distance between the said free end means of said external current-carrying element and the said free end means of said bus bar means, an elongated member extending transversely through apertures formed in said conductive means and through said bus bar means in the region of said free end means thereof and being in non-conductive relation therewith and retaining same in assembled relation, and manually adjustable means carried by said elongated member and adapted, wHen adjusted in one direction, to effect a gripping relation of said conductive means with said current carrying element when said connector assembly is in said extended position.
 10. A current take-off unit adapted to be removably connected to a current-carrying installation at an intermediate location between a source side current-carrying element and a load side current-carrying element, said unit being movable transversely of said source side and load side current-carrying elements into and out of position for aligned connection therewith, said unit comprising bus bar means, said bus bar means including first and second free end means at opposite ends thereof for end-to-end alignment with corresponding free end means of said source side current-carrying element and of said load side current carrying element respectively, said respective free end means terminating short of each other when in said end-to-end alignment, a connector assembly adjustably mounted on said bus bar means in the region of said first free end means for longitudinal movement between extended and retracted positions in relation to said first free end means, said connector assembly including conductive means adapted for electrically conductive engagement with said free end means of one of said source-side and said load side current-carrying elements when said connector assembly is in said extended position whereby said conductive means spans the distance between the said free end means of said current-carrying element and the first free end means of said bus bar means, an elongated member extending transversely through apertures formed in said conductive means and through said bus bar means in the region of said first free end means thereof and being in non-conductive relation therewith retaining same in assembled relation, and manually adjustable means carried by said elongated member and adapted, when adjusted in one direction, to effect a gripping relation of said conductive means with said current-carrying element when said connector assembly is in said extended position.
 11. A current take-off unit as set forth in claim 10, including a second of said connector assemblies adjustably mounted for connecting association between, and on one of, said second free end means of said bus bar means and the free end means of the other of said source-side and load-side current carrying elements.
 12. A current take-off unit as set forth in claim 9, wherein said conductive means include a pair of conductive jaw members, said jaw members being sandwiched between insulating means.
 13. A current take-off unit as set forth in claim 12, wherein said jaw members are elongated planar pieces of conductive material and are provided with aligned apertures through which the elongated member transversely extends, and said insulating means includes planar sections of insulating material disposed in face-to-face relation with the outer surfaces of said planar pieces, said planar sections being provided with apertures aligned with the apertures of said pieces and through which the elongated member transversely extends.
 14. A current take-off unit as set forth in claim 13, wherein said free end means of said bus bar means is provided with an elongated slot, said elongated member extending through said slot and being movable longitudinally thereof when said manually adjustable means carried by said elongated member is adjusted in a second direction.
 15. A current take-off unit as set forth in claim 13, wherein at least one planar section is provided with a protuberance which is adapted to extend transversely of a planar piece and abuttingly engage the other planar section when said planar pieces are in gripping engagement with the external current-carrying element.
 16. A current take-off unit as set forth in claim 13, wherein said aperture formed in each planar piece is sized to accommodate a protruding collar formed on the adjacent planar section, said collar delimiting the aligned aperture formed in said aDjacent planar section.
 17. A current take-off unit as forth in claim 9, wherein said bus bar means includes a plurality of elongated bus bars arranged in spaced substantially parallel relation, elongated lontigudinally extending slots in the free ends of each of said bus bars, said connector assembly including a pair of conductive jaw members for each bus bar, each pair of jaw members being separated from an adjacent pair of jaw members by insulating means.
 18. A current take-off unit as set forth in claim 17, wherein said insulating means includes a planar section of insulating material disposed intermediate adjacent pairs of jaw members, said planar section being provided with an aperture through which transversely extends the elongated member, said planar section aperture being delimited by a protruding collar which extends into the aligned aperture formed in the adjacent jaw member. 